The invention relates to a vehicle brake system, and more particularly, to an improvement of a brake system with an automatic brake controller which actuates a brake booster without operating a brake pedal.
A brake system with an automatic brake controller which actuates a brake booster without the depression of a brake pedal is known in the art (see Japanese Laid-Open Paten Applications No. 262,958/1992 and No. 215,156/1986).
The first cited Application discloses an automatic brake controller including a solenoid disposed within a valve body, and an arrangement is made such that when the solenoid is operated, a valve mechanism is operated in response thereto. Thus, operating the solenoid is effective to actuate a brake booster without depressing a brake pedal.
The second cited Application discloses an automatic brake controller including a solenoid operated open/close valve which is operable to introduce a pressure fluid selectively into a variable pressure chamber. Thus, when the valve is operated, the pressure fluid is introduced into the variable pressure chamber to allow a brake booster to be actuated to function as an automatic brake without the depression of a brake pedal.
Such an automatic brake controller suffers from a likelihood that the brake booster may be accidentally actuated, though not required, as a result of a failure in an electrical system or that the operation of the automatic brake may not be terminated due to an electrical or mechanical failure despite an intended braking operation has taken place satisfactorily.
Such an accidental actuation of the automatic brake may introduce the risk of a collision by a following vehicle, and a failure to terminate the operation of the automatic brake may result in a difficulty to keep running a vehicle, both representing drawbacks.
In view of the foregoing, according to a first aspect of the invention, there is provided a brake system including a brake booster actuated in response to the operation of a brake operating member, an automatic brake controller adapted to actuate the brake booster without the operation of the brake operating member upon fulfillment of a given requirement, a master cylinder operated upon by an output from the brake booster, and a wheel cylinder operated upon by an output liquid pressure from the master cylinder for developing a braking force;
the brake system comprising a safety mechanism which comprises brake operation detecting means for detecting an operation of the braking operating member, automatic brake actuation command signal detecting means for detecting an actuation command signal to the automatic brake controller, and brake output detecting means for detecting whether or not the braking force is being developed, the arrangement being such that a communication between the master cylinder and the wheel cylinder is interrupted while decompressing the output liquid pressure introduced into the wheel cylinder in the event of an abnormality that the brake output detecting means detects the development of the braking force when neither the brake operation detecting means detects the operation of the brake operating member nor the automatic brake actuation command signal detecting means detects the automatic brake command signal.
According to a second aspect of the invention, there is provided a brake system including a brake booster actuated in response to the operation of a brake operating member, an automatic brake controller adapted to actuate the brake booster without the operation of the brake operating member upon fulfillment of a given requirement, a master cylinder operated upon by an output from the brake booster, and a wheel cylinder operated upon by an output liquid pressure from the master cylinder for developing a braking force;
the brake system comprising a safety mechanism which comprises accelerator operation detecting means for detecting an operation of an accelerator pedal, automatic brake actuation command signal detecting means for detecting an actuation command signal to the automatic brake controller, and brake output detecting means for detecting whether or not the braking force is being developed, the arrangement being such that a communication between the master cylinder and the wheel cylinder is interrupted while decompressing the output liquid pressure introduced into the wheel cylinder in the event of an abnormality that the brake output detecting means detects the development of the braking force when the automatic brake actuation command signal detecting means does not detect the actuation command signal and the accelerator operation detecting means detects the operation of the accelerator pedal.
According to the first aspect of the invention, in the event of abnormality that the automatic brake is accidentally actuated when no braking operation is required, the safety mechanism detects such occurrence to terminate the automatic brake, thus avoiding the risk of a collision by succeeding vehicle. Also, in the event of an abnormality that the automatic brake can not be terminated, such occurrence is detected by the safety mechanism, which again terminates the automatic brake, thus allowing a vehicle to continue running.
According to the second aspect of the invention, the provision of the accelerator operation detective means allows the operation of the automatic brake to be terminated upon start-up or acceleration of a vehicle where no operation of the automatic brake is required, thus enabling a smooth start-up or acceleration of the vehicle.
Above and other objects, features and advantages of the invention will become apparent from the following description of the embodiments thereof with reference to the attached drawings.